Quadratic and inversely proportionalThe higher the velocity, the lower the pressure (by a square root)

What is the continuity equation?

What is the relationship between area and velocity?

Inversely proportionalMore stenotic a valve, the greater the flow velocityFlow velocity is INVERSELY related to cross sectional area (CSA)

6

How do we apply the Bernoulli theorem?

Allows us to enable calculation of valve orifice area from measurements of pressure and flow rateFirst we record pressure difference and use it to correlate with velocity (quadratic and directly proportional)Then we get flow rate and take flow rate/flow velocity = cross sectional area

What is the Gorlin Valve area equation?

A = F/ [C*44.3*sqr(P1-P2)]

Why is chamber upstream of the high velocity low CSA stenotic valve subjected to higher pressure?

Because the upstream chamber is MAINTAINED at a higher pressure (think of squeezing a balloon full of fluid through a starbucks straw-fluid through the starbucks straw might have high ass velocity, but it takes the balloon longer to get rid of the fluid due to the increase in resistance-increase in resistance (as seen by stenotic valve) leads to decrease in flow -therefore, your upstream balloon (LV) is subjected to higher pressures for longer

13

What are the key observations from the valve area relationship?

In order to Increase blood flow across stenotic aortic valve, you will require a large increase in pressure gradient (and thus more systolic pressure load on LV)

14

Why must you always calculate pressure gradient and CO to determine orifice area?

At low rates, even with a small valve orifice area, the valve pressure gradient may be deceptively small (flow rate and pressure relationship)Valve area must always be calculated using the pressure gradient and cardiac output (flow) to determine what is deficient

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What are the key characteristics of stenotic valves?

Cannot respond well to increased demandCO is impaired

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What are the consequences of increasing blood flow across stenotic valve?

What are the key characteristics of mitral stenosis?

MStenosis is adversely affected by increases in heart rateThe less filling time = the less time LA and LV can equilibrateTherefore, for a patient with MStenosis, you want to reduce HRDegree of decay of inflow velocity decreases as duration of diastole decreases (slide 41)

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Why is increasing heart rate contraindicated in Mstenosis?

Because there is less filling time to allow LA and LV to equilibrateThis does not affect LV in AS because the diastolic filling is normal (since mitral valve works)

34

What are the mild, moderate and critical sizes for Mstenosis?

2.0 cm^21.5^21.0^2Smaller CSA is not as well tolerated in Mstenosis in comparison to AStenosis

35

What does the heart do to adapt to mitral stenosis?

NOTHING There are no compensatory mechanisms lol (slide 46 is intentionally blank)

36

What are the consequences of no heart compensatory mechanism in severe MS?

Why do you get pulmonary venous HTN in Mstenosis?

Why do you get pulmonary arterial HTN? What are the consequences?

1. increase LA pressure leads to increased pulm artery pressure2. Increased LA pressure leads to increased pulmonary arteriolar constriction -can lead to obliterative PA destruction of PA pressure elevated for too long (which would then lead to irreversible PVR increase and decreased PBF3. Severe right ventricular afterload excess -may eventually lead to RV dilation, tricuspid regurg and systemic venous HTN4. The back up from right side of the heart may lead to hepatic dysfunction, edema and ascites

40

What is the clinical course of mitral stenosis?

Lack of cardiac adaptation = patients become symptomatic much faster

41

What are the predominant symptoms of MS?

1. dyspnea on exertion due to LA pressure elevation2. fatigue due to sustained low CO

42

What is the difference between MStenosis and AS?

Patients with symptoms for MS do not deteriorate rapidly like AS patients due -gradual progression over many years as severity of valve obstruction slowly increasesDue to lack of adaptive mechanisms in MS as opposed to AS, you become symptomatic with mild/moderate severities

What are the key characteristics of RV failure secondary to Tricuspid Regurg?

When you have too much pulm vascular resistance (perhaps from obliterative disease), your tricuspid valve leaks fluid backSeverely increases RV and thus RA pressureThus you get ascites, edema and hepatic dysfunction as a resultAnother variant of MStenosis